This invention relates to a drilling machine and particularly to a variable speed transmission mechanism and a feeding mechanism for a drilling member of a drilling machine.
FIG. 1 shows a conventional drilling machine which includes a vertical post 2 mounted on a base 1 and a top housing 3 mounted on the post 2. To the lower side of the housing 3 is mounted a drilling member 4. A motor 5 is mounted in the housing 3 with a driving pulley 5a on its shaft. The driving pulley 5a is connected to a driven pulley 4a through a transmission belt 6 so that the output rotation of the motor is transmitted to the drilling member 4. The pulleys used in this machine are step pulleys so that the speed of the transmission belt is adjustable. However, when it is desired to change the speed of the drilling member 4 it is necessary to change the position of the belt 6 by detaching the belt from one of the grooves of a step pulley and then placing it in an other groove. This adjustment is inconvenient. The drilling member 4 is connected to a splined shaft (not shown) which is associated with a splined sleeve member so that the drilling member 4 can be moved downward or upward while rotating. The drilling member 4 is also provided with a rack which is associated with a pinion 7a. The pinion 7a is mounted on an operating shaft which is connected to an operating handle 7. By operating the handle 7, the drilling member can be fed from the machine or withdrawn from a workpiece. In this machine, the transmission mechanism required to rotate the drilling member while allowing the drilling member to move up and down is complicated and also expensive because of the use of the splined shaft and the splined sleeve.